---
title: Docker and private modules
redirect_from:
  - /private-modules/docker-and-private-modules
---

To install private npm packages in a Docker container, you will need to use [Docker build secrets](https://docs.docker.com/build/building/secrets/#types-of-build-secrets).

## Background: runtime variables

You cannot install private npm packages in a Docker container using only runtime variables. Consider the following Dockerfile:

```
FROM node

COPY package.json package.json
RUN npm install

# Add your source files
COPY . .
CMD npm start
```

Which will use the official [Node.js](https://hub.docker.com/_/node) image, copy the `package.json` into our container, installs dependencies, copies the source files and runs the start command as specified in the `package.json`.

In order to install private packages, you may think that we could just add a line before we run `npm install`, using the [ENV parameter](https://docs.docker.com/engine/reference/builder/#env):

```docker
ENV NPM_TOKEN=00000000-0000-0000-0000-000000000000
```

However, this doesn't work as you would expect, because you want the npm install to occur when you run `docker build`, and in this instance, `ENV` variables aren't used, they are set for runtime only.

Instead of run-time variables, you must use Docker build secrets.

## Update the Dockerfile

The Dockerfile that takes advantage of this has a few more lines in it than the earlier example that allows us to use your global `.npmrc` and the access token created when running `npm login` command (if you haven't run it already - do so before moving on).

```dockerfile
# https://docs.npmjs.com/docker-and-private-modules
FROM node:18

ENV APP_HOME="/app"

WORKDIR ${APP_HOME}

COPY package*.json ${APP_HOME}/

RUN --mount=type=secret,id=npmrc,target=/root/.npmrc npm install

COPY . ${APP_HOME}/

CMD npm start

```

This will configure your Dockerfile to receive `.npmrc` file via build secrets, that will leave no trace after npm dependency installation is done.

## Build the Docker image

To build the image using the above Dockerfile and the npm authentication token, you can run the following command. Note the `.` at the end to give `docker build` the current directory as an argument.

```shell
docker build . -t secure-app-secrets:1.0 --secret id=npmrc,src=$HOME/.npmrc
```

This will build the Docker image with the access token coming from your global `.npmrc` file received via build secrets, so you can run `npm install` inside your container as the current logged-in user.

<Note>

**Note:** You may need to specify a working directory different from the default `/` otherwise some frameworks like Angular will fail.

</Note>
